Project Summary S. aureus is responsible for a large number of infections in the community and healthcare setting. Especially as the number and incidence of antibiotic resistant strains continue to rise, the need for alternative intervention methods is becoming increasingly critical. A strategy to develop novel therapies is to identify and block host pathways exploited by pathogens to cause disease. Autophagy is one such pathway. Autophagy is a highly conserved, ubiquitous cellular process in which a double membrane autophagosome engulfs damaged cytosolic components and targets them for lysosomal degradation; however, recent research has demonstrated its critical role in pathogen tolerance and clearance. Experiments performed in collaboration between the Cadwell and Torres labs demonstrated a vital role for ATG16L1, a protein that mediates autophagosome formation, in S. aureus tolerance. Using an in vivo model of autophagy loss where ATG16L1 is almost completely abolished, the increased susceptibility to lethal challenge was found to be dependent on the production of the S. aureus virulence factor, ?-toxin. Upon further experimentation, it was shown that endothelial cells lacking ATG16L1 display higher levels of the plasma membrane ?-toxin receptor ADAM10. These data suggest autophagy plays a negative regulatory role on ADAM10. However, it is remains unclear how autophagy, a cytosolic degradation pathway, regulates the levels of membrane bound ADAM10. Our aim is to identify host factors, mechanisms, and/or pathways that are differentially regulated by autophagy that affect ADAM10 levels. Using an in vitro system that we developed for this purpose, our initial data suggests that ATG16L1 regulates ADAM10 independently of the lysosome or proteasome. Instead, cells lacking ATG16L1 show decreased production of extracellular vesicles containing ADAM10. We plan to continue to test precisely how ATG16L1 and autophagy influence native localization of ADAM10; particularly through packaging into vesicles meant for extracellular release, trafficking to the plasma membrane, and endocytic internalization. Additionally, our goal is to determine the amino acid motifs or structural elements of ADAM10 that confer its autophagy dependent regulation. Each one of these strategies is an attempt to better understand the biology of ADAM10 regulation by autophagy as this pathway and its substrates may serve as alternative targets for treatment of S. aureus infections and other conditions involving the endothelial barrier.